Method and apparatus for measuring bioimpedance

ABSTRACT

A method and an apparatus for measuring a bioimpedance are disclosed. The apparatus includes a first electrical signal generator configured to generate a first electrical signal to measure a bioimpedance of an object. The apparatus also includes a compensation signal generator configured to generate a compensation signal to compensate a biosignal measured based on the first electrical signal, and an amplifier configured to amplify the compensated biosignal.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit under 35 USC § 119(a) of KoreanPatent Application No. 10-2014-0090620, filed on Jul. 17, 2014, in theKorean Intellectual Property Office, the entire disclosure of which isincorporated herein by reference for all purposes.

BACKGROUND

1. Field

The following description relates to a method and an apparatus tomeasure bioimpedance.

2. Description of Related Art

Skin, blood, muscles, tissues, joints, and other portions or organs of abody produce an impedance with a value including a resistance componentand a capacitor component in response to current flowing through thebody. The impedance value refers to a bioimpedance. Based on thebioimpedance, body fat or body fluid components may be estimated. Thebioimpedance is obtained by applying a low-frequency current signal to abody of a user and measuring a voltage signal between measurementelectrodes.

A bioelectrode used to measure the bioimpedance includes a wet electrodeand a dry electrode. The wet electrode uses an electrolyte solution forsurface treatment to reduce an interface impedance of a surface on whichthe electrode and skin of the user are contacted. Conversely, the dryelectrode does not use an electrolyte to measure a biosignal, forexample, the bioimpedance. As a result, the dry electrode has a greaterinterface impedance than the wet electrode.

SUMMARY

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used as an aid in determining the scope of the claimed subjectmatter.

In accordance with an illustrative example, there is provided anapparatus to measure a bioimpedance, the apparatus including a firstelectrical signal generator configured to generate a first electricalsignal to measure a bioimpedance of an object; a compensation signalgenerator configured to generate a compensation signal to compensate abiosignal measured based on the first electrical signal; and anamplifier configured to amplify the compensated biosignal.

The compensation signal may include a phase opposite to a phase of thebiosignal, and an amplitude of the compensated biosignal may be smallerthan an amplitude of the biosignal before the compensation.

The biosignal may be generated based on the first electrical signal andthe bioimpedance.

The compensation signal generator may include a second electrical signalgenerator configured to generate a second electrical signal including aphase identical to or opposite to a phase of the first electricalsignal.

The compensation signal generator may be configured to output thecompensation signal generated in response to the second electricalsignal flowing from electrodes into the object.

A distance between two electrodes applying the second electrical signalinto the object may be shorter than a distance between two electrodesmeasuring the biosignal.

The compensation signal generator further may include an impedanceelement configured to generate the compensation signal based on thesecond electrical signal.

The compensation signal generator may be configured to adjust anamplitude of the second electrical signal based on an amplitude of thecompensation signal.

The apparatus may also include a connection adjustor configured toadjust connections between electrodes electrically connected to theobject, the first electrical signal generator, and the amplifier; and acontroller configured to output a control signal to control a connectionbetween switches included in the connection adjustor.

The connection adjustor may adjust, based on the control signal,connections among terminals connected to the electrodes, terminalsconnected to the first electrical signal generator, and terminalsconnected to the amplifier.

The apparatus may also include a first capacitor between an electrode,at which the biosignal is measured, and a node, at which the biosignaland the compensation signal are combined; and a second capacitor betweena node, at which the compensation signal is output, and the node, atwhich the biosignal and the compensation signal are combined.

The apparatus may also include electrodes configured to conduct thefirst electrical signal or the biosignal to the object, and wherein atleast one of the electrodes interfaces with the object in electricalregions.

The compensation signal generator may generate the compensation signalin response to the second electrical signal flowing through the objectto compensate a biosignal generated based on the first electrical signalflowing through the object and based on an interface impedance betweenthe object and electrodes.

In accordance with another illustrative example, there is provided anapparatus to measure a bioimpedance, the apparatus including anelectrical signal generator configured to generate an electrical signalto measure a bioimpedance of an object; an amplifier configured toamplify a biosignal measured based on the electrical signal; and aconnection adjustor configured to adjust connections between electrodeselectrically connected to the object, the electrical signal generator,and the amplifier.

The connection adjustor may be configured to determine, among theelectrodes, an electrode to which the electrical signal generated istransmitted based on a control signal.

In accordance with an illustrative example, there is provided a methodof measuring a bioimpedance, the method including generating a firstelectrical signal to measure a bioimpedance of an object; generating acompensation signal to compensate for a biosignal generated based on thefirst electrical signal and the bioimpedance; and amplifying thecompensated biosignal.

The compensated biosignal may include an amplitude smaller than anamplitude of the biosignal prior to compensation.

The outputting of the compensation signal may include generating asecond electrical signal including a phase identical or opposite to aphase of the first electrical signal; and measuring a biosignalgenerated in response to the second electrical signal flowing into theobject and thereby flowing in the object, and outputting the measuredbiosignal as the compensation signal.

A distance between two electrodes applying the second electrical signalto the object may be shorter than a distance between two electrodesmeasuring the biosignal.

The outputting of the compensation signal may include generating asecond electrical signal including a phase identical or opposite to aphase of the first electrical signal; and outputting, as thecompensation signal, an electrical signal generated in response to thesecond electrical signal flowing through an impedance element, andwherein the biosignal is combined with the compensation signal todecrease an amplitude of the biosignal.

Other features and aspects will be apparent from the following detaileddescription, the drawings, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects will become apparent and more readilyappreciated from the following description of the embodiments, taken inconjunction with the accompanying drawings in which:

FIGS. 1A and 1B are diagrams illustrating an example of a configurationof a bioimpedance measuring apparatus, in accordance with an embodiment.

FIG. 2 is a diagram illustrating an example of an operation of thebioimpedance measuring apparatus, in accordance with an embodiment.

FIGS. 3 and 4 are diagrams illustrating examples of bioelectrodes, inaccordance with an embodiment.

FIGS. 5 and 6 are diagrams illustrating examples of other bioelectrodes,in accordance with an embodiment.

FIGS. 7A and 7B are diagrams illustrating another example of aconfiguration of a bioimpedance measuring apparatus, in accordance withan embodiment.

FIG. 8 is a diagram illustrating another example of an operation of thebioimpedance measuring apparatus, in accordance with an embodiment.

FIG. 9 is a diagram illustrating, using a signal waveform, an example ofa process in which a compensation signal compensates a biosignalmeasured from an object, in accordance with an embodiment.

FIG. 10 is a diagram illustrating a still another example of anoperation of a bioimpedance measuring apparatus, in accordance with anembodiment.

FIG. 11 is a diagram illustrating an example of an operation of abioimpedance measuring apparatus including a connection adjustor, inaccordance with an embodiment.

FIG. 12 is a diagram illustrating another example of an operation of abioimpedance measuring apparatus including a connection adjustor, inaccordance with an embodiment.

FIG. 13 is a flowchart illustrating an example of a bioimpedancemeasuring method, in accordance with an embodiment.

Throughout the drawings and the detailed description, unless otherwisedescribed or provided, the same drawing reference numerals will beunderstood to refer to the same elements, features, and structures. Thedrawings may not be to scale, and the relative size, proportions, anddepiction of elements in the drawings may be exaggerated for clarity,illustration, and convenience.

DETAILED DESCRIPTION

The following detailed description is provided to assist the reader ingaining a comprehensive understanding of the methods, apparatuses,and/or systems described herein. However, various changes,modifications, and equivalents of the systems, apparatuses and/ormethods described herein will be apparent to one of ordinary skill inthe art. Also, descriptions of functions and constructions that are wellknown to one of ordinary skill in the art may be omitted for increasedclarity and conciseness.

Throughout the drawings and the detailed description, the same referencenumerals refer to the same elements. The drawings may not be to scale,and the relative size, proportions, and depiction of elements in thedrawings may be exaggerated for clarity, illustration, and convenience.

The features described herein may be embodied in different forms, andare not to be construed as being limited to the examples describedherein. Rather, the examples described herein have been provided so thatthis disclosure will be thorough and complete, and will convey the fullscope of the disclosure to one of ordinary skill in the art.

It will be understood that when an element or layer is referred to asbeing “on” or “connected to” another element or layer, it can bedirectly on or connected to the other element or layer or throughintervening elements or layers may be present. In contrast, when anelement is referred to as being “directly on” or “directly connected to”another element or layer, there are no intervening elements or layerspresent. Like reference numerals refer to like elements throughout. Asused herein, the term “and/or” includes any and all combinations of oneor more of the associated listed items.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the presentinvention. As used herein, the singular forms “a,” “an” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“comprises” and/or “comprising,” when used in this specification,specify the presence of stated features, integers, steps, operations,elements, and/or components, but do not preclude the presence oraddition of one or more other features, integers, steps, operations,elements, components, and/or groups thereof.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which the present invention belongs. Itwill be further understood that terms, such as those defined in commonlyused dictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art andwill not be interpreted in an idealized or overly formal sense unlessexpressly so defined herein.

FIGS. 1A and 1B are diagrams illustrating an example of a configurationof a bioimpedance measuring apparatus 110, in accordance with anembodiment. The bioimpedance measuring apparatus 110 illustrated inFIGS. 1A and 1B measure a bioimpedance of an object 160. The object 160may include a human or animal organ, tissue, muscle, veins, or otherportion of a human body or animal body. A type of the bioimpedance mayvary. For example, the bioimpedance includes a bioimpedance indicating aresistance degree in the skin, a bioimpedance indicating a hydrationdegree of the skin, a bioimpedance that varies depending on pulmonaryrespiration, a bioimpedance that varies depending on blood flow, abioimpedance present on an electrical path through the skin and ameasurement electrode, a bioimpedance indicating an activation degree ofa sympathetic nerve, and the like.

The bioimpedance measured by the bioimpedance measuring apparatus 110may be used to estimate a body fat content of the object 160. Thebioimpedance measuring apparatus 110 may be implemented in a variety ofwearable devices. For example, the bioimpedance measuring apparatus 110may be included in a wearable device such as a watch, a glove, clothing,a hat, or a shoe. The bioimpedance measuring apparatus 110 converts themeasured bioimpedance to biodata suitable for the wearable device toprocess and transmits the converted bioimpedance to the wearable device.The wearable device then analyzes the body fat components of the object160 based on the biodata received from the bioimpedance measuringapparatus 110 and provides a result of the analyzing to a user.

In an example, to measure the bioimpedance, the bioimpedance measuringapparatus 110 applies, using an electrode, a current signal having afrequency component to the object 160, for example, a body of the user.Using another electrode, the bioimpedance measuring apparatus 110measures a voltage signal generated in response to the current signalflowing into the object 160 and thereby flowing through the object 160.For example, using an electrode, the bioimpedance measuring apparatus110 applies an alternating current (AC) signal having a frequencycomponent between a kilohertz (kHz) and 1 megahertz (MHz) to skin of theuser to measure the bioimpedance. Using another electrode, thebioimpedance measuring apparatus 110 measures an AC voltage signalgenerated by the AC signal and the bioimpedance. The bioimpedance of theobject 160 is estimated based on the current signal applied to theobject 160 and the voltage signal measured from the object 160.

In another example, to measure a bioimpedance, the bioimpedancemeasuring apparatus 110 applies, using an electrode, a voltage signalhaving a frequency component to the object 160. Using another electrode,the bioimpedance measuring apparatus 110 measures a current signalgenerated in response to the voltage signal flowing through the object160. The bioimpedance of the object 160 is estimated based on thevoltage signal applied to the object 160 and the current signal measuredfrom the object 160.

In measuring an electrical signal from the object 160 using anelectrode, the electrical signal to be measured may be affected by aninterface impedance, which is an impedance generated from an interfacebetween the electrode and skin and/or organ of the user. For example, adry electrode that measures a biosignal without using an electrolytesuch as a gel may have an interface impedance greater or considerablygreater than a bioimpedance to be measured. The dry electrode includes,for example, a metal electrode, a conductive rubber electrode, and acapacitive coupling electrode. In general, a magnitude of thebioimpedance to be measured is approximately several hundred ohms. As aresult, a measurement resolution that distinguishes an impedancedifference of approximately 0.5 ohm may be required. The dry electrodegenerally has an interface impedance of greater than or equal to 1 kiloohm.

As a magnitude of the interface impedance between the electrode and theskin of the user increases, a magnitude of the electrical signal to bemeasured from the object 160 also increases. An amplifier 150 thatamplifies the biosignal, which is the converted measured bioimpedance ofthe object 160 that is based on the voltage signal applied to the object160 and the current signal measured from the object 160, has a range ofinput electrical signals that can be amplified. The biosignal may bemeasured in a form of a voltage signal or a current signal, and includebioimpedance information.

When the measured biosignal is input to the amplifier 150, without beingadjusted, the biosignal deviating from an operational range of theamplifier 150 is input to the amplifier 150. A magnitude of thebiosignal is greater than the operation range of the amplifier 150 dueto the magnitude of the interface impedance. To offset a factor that maybe caused by the interface impedance on the biosignal measured from theobject 160, the bioimpedance measuring apparatus 110 compensates thebiosignal prior to being input to the amplifier 150 using a compensationsignal. Thus, the compensation signal decreases an amplitude of thebiosignal input to the amplifier 150 is decreased, within theoperational range of the amplifier 150. Accordingly, the bioimpedancemeasuring apparatus 110 prevents saturation of the amplifier 150 causedby an input of a biosignal measured from the object 160 having amagnitude or an amplitude exceeding the operational range of theamplifier 150 due to interface impedance. The bioimpedance measuringapparatus 110 measures a bioimpedance and compensates the biosignal.

In addition, the bioimpedance measuring apparatus 110 compensates thebiosignal measured from the object 160 and decreases the magnitude ofthe biosignal to enable a use of an analog-to-digital converter (ADC)having a lower measurement resolution. The ADC disposed at a signalprocessing terminal converts the biosignal amplified by the amplifier150 to a digital signal. When all impedances on a path through which abioimpedance is measured are smaller, a signal-to-noise ratio (SNR)required in the measurement circuit increases, and an effective numberof bits (ENOB) required in the ADC decreases. The bioimpedance measuringapparatus 110 reduces a magnitude of the all bioimpedances calculated onthe path by reducing a magnitude of the biosignal measured from theobject 160, and enables usage of a lower resolution ADC.

The magnitude of the interface impedance between the electrode and theskin of the user may vary depending on the number of users. Also, themagnitude of the interface impedance may vary depending on measuringenvironments, for example, a skin moisture level, a surface area of anelectrode, a temperature, and a pressure applied to an electrode. Thebioimpedance measuring apparatus 110 precisely measures a bioimpedanceby decreasing an influence of the interface impedance sensitivity on thebiosignal measured from the object 160.

Referring to FIG. 1A, the bioimpedance measuring apparatus 110 includesa first electrical signal generator 120, a compensation signal generator130, and the amplifier 150.

The first electrical signal generator 120 generates a first electricalsignal to measure a bioimpedance of the object 160. For example, thefirst electrical signal is an AC signal or an AC voltage signal having afrequency component. The first electrical signal generated by the firstelectrical signal generator 120 is applied to the object 160 throughelectrodes, for example, electrodes 165 and 180. An electrical path isformed between the first electrical signal generator 120, the object160, and the electrodes 165 and 180. The first electrical signal appliedto the object 160 flows through the formed electrical path. Thus, abiosignal is generated based on the first electrical signal flowing inthe object 160 and the bioimpedance. The generated biosignal is measuredthrough electrodes, for example, electrodes 170 and 175.

The electrodes 165, 170, 175, and 180 provide an interface between thefirst electrical signal, the biosignal, and the object 160. In anexample, at least one of the electrodes 165, 170, 175, and 180interfaces with the object 160 in electrical regions. Also, theelectrode 165 and the electrode 170 may include sub-electrodes havingrespective electrical regions, and the sub-electrodes of the electrode165 and the electrode 170 may be disposed in a mixed form, in a matrixform, in sequential form, or in parallel form. A detailed descriptionwill be provided with reference to FIGS. 5 and 6.

The compensation signal generator 130 generates a compensation signal tocompensate for the biosignal measured based on the first electricalsignal. The compensation signal has a phase opposite to a phase of thebiosignal, and an amplitude of the biosignal being compensated for bythe compensation signal is smaller than an amplitude of the compensationsignal. The compensation signal generator 130 uses an interfaceimpedance between the object 160 and electrodes, for example, 185 and190, to generate the compensation signal.

As illustrated in FIG. 1A, the compensation signal generator 130includes a second electrical signal generator 140. The second electricalsignal generator 140 generates a second electrical signal having a phaseopposite to a phase of the first electrical signal or a phase differenceof 180 degrees (°) from the phase of the first electrical signal. Thesecond electrical signal may be an AC signal having a frequencycomponent identical to the first electrical signal. The secondelectrical signal is applied to the object 160 through the electrodes185 and 190. The second electrical signal generator 140, the electrode185, the object 160, and the electrode 190 form an electrical path wherethe second electrical signal applied to the object 160 flows through theformed electrical path. The compensation signal is generated in responseto the second electrical signal flowing into the object 160 and therebyflowing through the object 160. Also, the compensation signal isgenerated in response to the second electrical signal flowing throughthe interface impedance between the object 160 and the electrodes 185and 190. The compensation signal generator 130 outputs, as thecompensation signal, a signal generated in response to the secondelectrical signal flowing into the object 160 through the electrodes 185and 190.

In an example, the first electrical signal and the second electricalsignal are current signals, and the biosignal and the compensationsignal are voltage signals. Conversely, in another example, the firstelectrical signal and the second electrical signal are voltage signals,and the biosignal and the compensation signal are current signals.

The electrodes 185 and 190 applying the second electrical signal to theobject 160 are disposed in close proximity to each other. To maximize aninfluence of the interface impedance between the object 160 and theelectrodes 185 and 190 and minimize an influence of the bioimpedance, adistance between the electrodes 185 and 190 applying the secondelectrical signal to the object 160 is designed to be shorter than adistance between the two electrodes 170 and 175 measuring the biosignalfrom the object 160.

The compensation signal is combined with the biosignal at an inputterminal of the amplifier 150. The biosignal is combined with thecompensation signal to decrease an amplitude of the biosignal by anamplitude of the compensation signal. The biosignal being compensatedfor by the compensation signal or a signal obtained by combining thebiosignal and the compensation signal is referred to as a combinationsignal. The amplitude of the biosignal decreases by combining thebiosignal and the compensation signal due to the biosignal and thecompensation signal having opposite phases. The biosignal beingcompensated for by the compensation signal includes, in one example,only an electrical signal with a bioimpedance factor because aninterface impedance factor almost identical to an interface impedancefactor between the object 160 and the electrodes 170 and 175 isreflected in the compensation signal.

As illustrated in FIG. 1A, first capacitors, for example, 125 and 135,are disposed between the electrodes 170 and 175 at which the biosignalis measured and nodes at which the biosignal and the compensation signalare combined. In addition, second capacitors, for example, 145 and 155,are disposed between nodes at which the compensation signal is outputand the nodes at which the biosignal and the compensation signal arecombined.

The compensation signal generator 130 adjusts the amplitude of thesecond electrical signal output from the second electrical signalgenerator 140 based on the amplitude of the compensation signal. Due toa measuring environment between the electrodes 170 and 175, and theobject 160 including noise and ambient and structural resistances, amagnitude of an interface impedance generated between the object 160 andthe electrodes 170 and 175 at which the biosignal is measured may differfrom a magnitude of an interface impedance generated between the object160 and the electrodes 185 and 190 at which the compensation signal isgenerated. In addition, the magnitude of the interface impedancegenerated between the object 160 and the electrodes 185 and 190 may varyat each point in time during measurement.

The amplitude of the compensation signal increases in proportion to themagnitude of the interface impedance generated between the object 160and the electrodes 185 and 190 and to the amplitude of the secondelectrical signal. When the amplitude of the compensation signal isdetermined to be higher than a predetermined threshold range, thecompensation signal generator 130 decreases the amplitude of thecompensation signal by decreasing the amplitude of the second electricalsignal output from the second electrical signal generator 140.Conversely, when the amplitude of the compensation signal is determinedto be lower than the predetermined threshold range, the compensationsignal generator 130 increases the amplitude of the compensation signalby increasing the amplitude of the second electrical signal output fromthe second electrical signal generator 140.

The combination signal of the biosignal and the compensation signal isinput to the amplifier 150, and the amplifier 150 amplifies thecombination signal. In one illustrative example, the combination signalis input to the amplifier 150 in a form of a differential signal. Forexample, an instrumentation amplifier (IA) that is widely used toamplify a biosignal is used as the amplifier 150. The bioimpedancemeasuring apparatus 110 outputs the amplified combination signal as anoutput signal.

In an example, the output signal from the amplifier 150 is demodulated.A control signal used to demodulate the output signal has a frequencycomponent used by the first electrical signal generator 120, and has asignal with or without a phase difference, as necessary. The outputsignal from the bioimpedance measuring apparatus 110 passes throughpost-processing, for example, filtering, and an analog-to-digitalconverter (ADC) converts the output signal to a digital signal. Thus,the bioimpedance of the object 160 is estimated by analyzing a digitalsignal. The estimated bioimpedance of the object 160 is then provided tothe user through a display device. The display device is a structuraldevice configured to output a numerical estimate of the bioimpedance ofthe object 160. The display device includes, but is not limited to, aliquid crystal display, a plasma display, a mobile phone, a tablet, orother similar display devices.

In another example, as illustrated in FIG. 1B, the second electricalsignal generator 140 generates a second electrical signal having a phaseidentical to a phase of the first electrical signal. The secondelectrical signal is an AC signal or an AC voltage signal having afrequency component and the phase identical to the first electricalsignal. The second electrical signal is applied to the object 160through the electrodes 185 and 190. The second electrical signal appliedto the object 160 generates the compensation signal, and thecompensation signal is combined with the biosignal. In FIG. 1B, aconnection between the node at which the compensation signal is outputand a signal line through which the biosignal is transmitted is oppositeto a corresponding connection illustrated in FIG. 1A. Also in FIG. 1B,the amplitude of the biosignal decreases when the biosignal is combinedwith the compensation signal having the phase opposite to the phase ofthe biosignal. Descriptions other than the foregoing may be the same asdescriptions provided with reference to FIG. 1A.

FIG. 2 is a diagram illustrating an example of an operation of abioimpedance measuring apparatus 210, in accordance with an embodiment.Referring to FIG. 2, the bioimpedance measuring apparatus 210 includes afirst electrical signal generator 220, a compensation signal generator230, and an amplifier 250. The compensation signal generator 230includes a second electrical signal generator 240.

The first electrical signal generator 220 generates a first electricalsignal, “ip” and “in,” to measure a bioimpedance. The generated firstelectrical signal is applied to an object, for example, a body of auser, through electrodes. An interface impedance may be generatedbetween the object and an electrode. As illustrated in FIG. 2, “Z_if1”through “Z_if6” indicate an equivalent model 270 of the interfaceimpedance generated between the object and each electrode. “Z_body1”through “Z_body4” indicate an equivalent model 260 of a bioimpedance ofthe object, and “Z_body2” among Z_body1 through Z_body4 indicates adesired bioimpedance to be measured. The biosignal is generated based onthe first electrical signal and the measured bioimpedance Z_body2. Thefirst electrical signal is output in a form of a current signal or avoltage signal. In one configuration, a voltage difference between anode “V_Vp” and a node “V_Vn” at which the biosignal is measured has avery large value due to the interface impedance, Z_if1 through Z_if4,having a large impedance value.

The compensation signal generator 230 generates a compensation signal todecrease an amplitude of the biosignal. The second electrical signalgenerator 240, in the compensation signal generator 230, generates asecond electrical signal, “ipd” and “ind,” having a phase identical oropposite to a phase of the first electrical signal. Identically to thefirst electrical signal, the second electrical signal is output in aform of a current signal or a voltage signal. Based on the phase of thesecond electrical signal, a combination relationship between thebiosignal and the compensation signal is different, and a detaileddescription may be found with reference to FIGS. 1A and 1B. The secondelectrical signal generated by the second electrical signal generator240 is applied to the object through an electrode.

As illustrated in FIG. 2, “Z_if5” and “Z_if6” indicate an equivalentmodel of an interface impedance generated between the object andelectrodes applying the second electrical signal to the object.“Z_body4” indicates a bioimpedance on a path through which the secondelectrical signal flows. The compensation signal generated based on thesecond electrical signal, the interface impedance Z_if5 and Z_if6, andthe bioimpedance Z_body4 is output from a node “V_Vpd” and a node“V_Vnd.”

The biosignal and the compensation signal are combined at an inputterminal of the amplifier 250. The compensation signal decreases anamplitude of the biosignal. Because the amplitude of a combinationsignal of the biosignal and the compensation signal is smaller than theamplitude of the biosignal and the amplitude of the compensation signal,the amplifier 250 is less likely to be saturated by the combinationsignal of the biosignal and the compensation signal. Thus, despite alarge value of the interface impedances Z_if1 through Z_if4, thebioimpedance measuring apparatus 210 amplifies the biosignal includingbioimpedance information without saturating the amplifier 250. In FIG.2, “V_ref_IA” 215 indicates a reference signal used to determine adirect current (DC) signal component of the input signal to theamplifier 250.

FIGS. 3 and 4 are diagrams illustrating an example of bioelectrodes, inaccordance with an embodiment.

FIG. 3 is a diagram illustrating an example of a bioelectrode 300including electrodes, for example, a first electrode 310, a secondelectrode 320, a third electrode 330, and a fourth electrode 340, thatapply a first electrical signal to an object or measure a biosignal fromthe object.

Referring to FIG. 3, the first electrode 310, the second electrode 320,the third electrode 330, and the fourth electrode 340 correspond to theelectrode 165, the electrode 170, the electrode 175, and the electrode180 illustrated in FIGS. 1A and 1B, respectively. The electrodes 310through 340 are made of a conductive material, and are wet electrodes ordry electrodes. Alternatively, the electrodes 310 through 340 arecapacitive coupling electrodes that measure a biosignal with a contactsurface with the object being insulated. Each electrode of thebioelectrode 300 has one electrical region.

FIG. 4 is a diagram illustrating electrically equivalent models betweenthe electrodes 310 through 340 illustrated in FIG. 3 and the object towhich the electrodes 310 through 340 are attached. Referring to FIG. 4,“Z_electrode1” 412 through “Z_electrode4” 418 are an equivalent model410 of an interface impedance generated between the object and each ofthe electrodes 310 through 340. “Z_body1” through “Z_body 3” are anequivalent model 420 of a bioimpedance of the object, and “Z_body2”among Z_body1 through Z_body 3 are a desired bioimpedance to bemeasured.

In FIG. 4, Z_electrode1 412 and Z_electrode2 414 have different valuesbased on a contact between the electrodes. Similarly, Z_electrode3 416and Z_electrode4 418 have different values based on a contact betweenthe electrodes. Thus, when measuring the bioimpedance Z_body2 using theelectrodes, a value to be measured may be greatly affected by thecontact between the electrodes.

FIGS. 5 and 6 are diagrams illustrating example of other bioelectrodes,in accordance with an embodiment.

FIG. 5 is a diagram illustrating an example of a bioelectrode 500including electrodes, for example, a first electrode 510, a secondelectrode 520, a third electrode 530, and a fourth electrode 540, thatapply a first electrical signal to an object or measure a biosignal fromthe object.

Referring to FIG. 5, the first electrode 510, the second electrode 520,the third electrode 530, and the fourth electrode 540 correspond to theelectrode 165, the electrode 170, the electrode 175, and the electrode180 illustrated in FIGS. 1A and 1B, respectively. The electrodes 510through 540 are made of a conductive material, and are wet or dryelectrodes. Alternatively, the electrodes 510 through 540 are capacitivecoupling electrodes that measure a biosignal with a contact surface withthe object being insulated.

Dissimilar to the bioelectrode 300 of FIG. 3, each of the electrodes 510through 540 of the bioelectrode 500 have electrical regions. Theelectrical regions of each electrode are electrically connected to oneanother.

An electrode may be attached to a portion of body skin of a user tomeasure a biosignal including a bioimpedance. The entire electrode or aportion thereof may be in contact with the skin. Thus, in thebioelectrode 300 of FIG. 3, the first electrode 310 and the secondelectrode 320 may be in contact with the skin at different locations.Also, different electrical conditions may be formed between the firstelectrode 310 and the second electrode 320.

However, in the bioelectrode 500 of FIG. 5, the first electrode 510 andthe second electrode 520 include sub-electrodes having respectiveelectrical regions, and sub-electrodes of the first electrode 510 andsub-electrodes of the second electrode 520 are disposed in a mixed form.In one alternative configuration, the sub-electrodes of the firstelectrode 510 and sub-electrodes of the second electrode 520 aredisposed in a series form, a parallel form, or a sequential form. Due tosuch an electrode structure, conditions for contact between the firstelectrode 510 and the skin and conditions for contact between the secondelectrode 520 and the skin may become considerably identical and; as aresult, a biosignal can be precisely measured. Similarly, the thirdelectrode 530 and the fourth electrode 540 include sub-electrodes havingrespective electrical regions, and sub-electrodes of the third electrode530 and sub-electrodes of the fourth electrode 540 are disposed in amixed form. In one alternative configuration, the sub-electrodes of thethird electrode 530 and sub-electrodes of the fourth electrode 540 aredisposed in a series form, a parallel form, or a sequential form.

FIG. 6 is a diagram illustrating electrically equivalent models betweenthe electrodes 510 through 540 illustrated in FIG. 5 and the object towhich the electrodes 510 through 540 are attached, in accordance with anembodiment. Referring to FIG. 6, “Z_electrode1” 612 through“Z_electrode4” 618 are an equivalent model 610 of an interface impedancegenerated between each of the electrodes 510 through 540 and the object.Also, “Z_body2” is an equivalent model 620 of a bioimpedance of theobject, and “Z_body2” is a desired bioimpedance to be measured.

Due to the electrode structure, the first electrode 510 and the secondelectrode 520 of FIG. 5 may have identical conditions for contact and;thus, “Z_electrode1” 612 and “Z_electrode2” 614 may be identical.Similarly, due to the electrode structure, the third electrode 530 andthe fourth electrode 540 of FIG. 5 may have identical conditions forcontact and; thus, “Z_electrode3” 616 and “Z_electrode4” 618 may beidentical.

In a case that Z_electrode1 612 and Z_electrode2 614 are identical,values of Z_electrode1 612 and Z_electrode2 614 are estimated byapplying a current signal to the object, such as the object 160illustrated in FIG. 1A, through a node of the first electrode 510 and anode of the second electrode 520 and measuring a difference in voltagesignals to be generated. Similarly, in a case that Z_electrode3 616 andZ_electrode4 618 are identical, values of Z_electrode3 616 andZ_electrode4 618 are estimated by applying a current signal to theobject through a node of the third electrode 530 and a node of thefourth electrode 540 and measuring a difference in voltage signals to begenerated. Subsequently, a summed value of Z_electrode2 614, Z_body2,and Z_electrode3 616 (Z_electrode2+Z_body2+Z_electrode3) is estimated byapplying a current signal to the object through the node of the firstelectrode 510 and the node of the fourth electrode 540 and measuringvoltage signals through the node of the second electrode 520 and thenode of the third electrode 530. In such an example, values ofZ_electrode2 614 and Z_electrode3 616 are previously estimated andknown. Therefore, a value of Z_body2 is calculated based on a sum of(Z_electrode2+Z_body2+Z_electrode3).

FIGS. 7A and 7B are diagrams illustrating another example of aconfiguration of a bioimpedance measuring apparatus 710, in accordancewith an embodiment. Referring to FIG. 7A, the bioimpedance measuringapparatus 710 includes a first electrical signal generator 720, acompensation signal generator 730, and an amplifier 750. Thecompensation signal generator 730 includes a second electrical signalgenerator 740 and an impedance element 745.

The first electrical signal generator 720 generates a first electricalsignal to measure a bioimpedance of an object 790. The first electricalsignal is an AC signal or an AC voltage signal having a frequencycomponent. The first electrical signal generated by the first electricalsignal generator 720 is applied to the object 790 through electrodes,for example, electrodes 765 and 780. The first electrical signalgenerator 720 and the electrodes 765 and 780 form an electrical path forthe first electrical signal to flow through the object 790. A biosignalmay then be generated based on the first electrical signal flowingthrough the object 790 and the bioimpedance of the object 790. Thebiosignal is measured through electrodes, for example, 770 and 775.

The compensation signal generator 730 generates a compensation signal tocompensate for the biosignal. The compensation signal has a phaseopposite to a phase of the biosignal. An amplitude of the biosignalbeing compensated for by the compensation signal is smaller than anamplitude of the compensation signal. The compensation signal generator730 generates the compensation signal based on a second electricalsignal generated at the second electrical signal generator 740. Thesecond electrical signal generator 740 generates the second electricalsignal having a phase opposite to a phase of the first electrical signalor a phase difference of 180° from the first electrical signal. Thesecond electrical signal may be an AC signal or an AC voltage signalhaving a frequency component identical to the first electrical signal.

The compensation signal generator 730 generates the compensation signalbased on the second electrical signal generated at the second electricalsignal generator 740 and the impedance element 745. The compensationsignal is generated in response to the second electrical signal flowingthrough the impedance element 745. In one example, the impedance element745 may have an impedance value of a predetermined magnitude. In oneexample, the impedance value of the impedance element 745 is designed tobe similar to a value of an interface impedance between the electrodesand the object 790. A passive device, for example, a resistor and acapacitor, may be used as the impedance element 745.

The compensation signal output from the compensation signal generator730 is combined with the biosignal at an input terminal of the amplifier750. As a result of the combination of the biosignal and thecompensation signal, the amplitude of the biosignal decreases by theamplitude of the compensation signal. The amplitude of the biosignaldecreases through the combination of the biosignal and the compensationsignal having opposite phases.

As illustrated in FIG. 7A, first capacitors, for example, 725 and 735,are disposed between the electrodes 770 and 775 at which the biosignalis measured and nodes at which the biosignal and the compensation signalare combined. Also, second capacitors, for example, 755 and 760, aredisposed between nodes at which the compensation signal is output andthe nodes at which the biosignal and the compensation signal arecombined.

The compensation signal generator 730 adjusts an amplitude of the secondelectrical signal output from the second electrical signal generator 740based on the amplitude of the compensation signal. In one illustrativeexample, the amplitude of the compensation signal increases inproportion to the amplitude of the second electrical signal and theimpedance value of the impedance element 745. When the amplitude of thecompensation signal is determined to be higher than a predeterminedthreshold range, the compensation signal generator 730 decreases theamplitude of the compensation signal by decreasing the amplitude of thesecond electrical signal output from the second electrical singlegenerator 740. Conversely, when the amplitude of the compensation signalis determined to be lower than the predetermined threshold range, thecompensation signal generator 730 increases the amplitude of thecompensation signal by increasing the second electrical signal outputfrom the second electrical signal generator 740.

A combination signal of the biosignal and the compensation signal areinput to the amplifier 750. The amplifier 750 amplifies the combinationsignal. The bioimpedance measuring apparatus 710 outputs the amplifiedcombination signal as an output signal. The bioimpedance measuringapparatus 710 processes a signal having a greater level by decreasing anamplitude of an input signal input to the amplifier 750 and amplifyingthe signal with the decreased amplitude. In addition, the bioimpedancemeasuring apparatus 710 improves accuracy in the measurement of abioimpedance by reducing an influence of an interface impedance valuethat varies with objects or at each point in time of measurement.

Referring to FIG. 7B, the second electrical signal generator 740generates a second electrical signal having a phase identical to a phaseof a first electrical signal. The second electrical signal is an ACsignal or an AC voltage signal having a frequency component and a phaseidentical to the first electrical signal. A compensation signal isgenerated in response to the second electrical signal flowing throughthe impedance element 745. The compensation signal is input to theamplifier 750 subsequent to being combined with a biosignal. In FIG. 7B,a connection between a node at which the compensation signal is outputand a signal line through which the biosignal is transmitted is oppositeto a corresponding connection illustrated in FIG. 7A. Also, in FIG. 7B,an amplitude of the biosignal decreases when the biosignal and thecompensation signal have a phase opposite to a phase of the biosignalare combined. Descriptions other than the foregoing may be the same asdescriptions provided with reference to FIG. 7A and; thus, repeateddescriptions shall be omitted for conciseness.

FIG. 8 is a diagram illustrating another example of an operation of abioimpedance measuring apparatus 810, in accordance with an embodiment.Referring to FIG. 8, the bioimpedance measuring apparatus 810 includes afirst electrical signal generator 820, a compensation signal generator830, and an amplifier 860. The compensation signal generator 830includes a second electrical signal generator 840 and an impedanceelement, “Z_dummy,” 850.

The first electrical signal generator 820 generates a first electricalsignal, for example, “ip” and “in,” to measure a bioimpedance of anobject. The generated first electrical signal is applied to the objectthrough a plurality of electrodes. “Z_if1” through “Z_if4” are anequivalent model 880 of an interface impedance generated between theelectrodes and the object. “Z_body1” through “Z_body3” are an equivalentmodel 870 of a bioimpedance of the object, and “Z_body2” among Z_body1through Z_body3 indicates a desired bioimpedance to be measured. Abiosignal is generated based on the first electrical signal and thebioimpedance Z_body2 to be actually measured. A voltage differencebetween a node “V_Vp” and a node “V_Vn” at which the biosignal ismeasured may have a considerably large value due to the interfaceimpedance Z_if1 through Z_if4 having a large impedance value.

The compensation signal generator 830 generates a compensation signal todecrease an amplitude of the biosignal. The second electrical signalgenerator 840 included in the compensation signal generator 830generates a second electrical signal, for example, “ipd” and “inp,”having a phase identical or opposite to a phase of the first electricalsignal. Based on the phase of the second electrical signal, acombination relationship between the biosignal and the compensationsignal may vary. A detailed description of the combination relationshipbetween the biosignal and the compensation signal is found withreference to FIGS. 7A and 7B. The second electrical signal generated bythe second electrical signal generator 840 flows through both terminalsof the impedance element Z_dummy 850. The impedance of the elementZ_dummy 850 and the second electrical signal generate the compensationsignal. The compensation signal is output from a node “V_Vpd” and a node“V_Vnd.” The impedance element Z_dummy 850 may have an impedance valuecorresponding to the interface impedance Z_if1 through Z_if4.

The biosignal and the compensation signal are combined at an inputterminal of the amplifier 860. As a result, the compensation signaldecreases the amplitude of the biosignal. The amplifier 860 amplifies acombination signal of the biosignal and the compensation signal. In FIG.8, “V_ref_IA” 865 indicates a reference signal used to determine a DCsignal component of an input signal to the amplifier 860.

FIG. 9 is a diagram illustrating, using a signal waveform, an example ofa process in which a compensation signal compensates a biosignalmeasured from an object, in accordance with an embodiment. Referring toa graph of FIG. 9, a first reference line 910 indicates a level of aninput signal with which an amplifier operates. For example, when aninput signal at a level exceeding the first reference line 910 is inputto the amplifier, the amplifier is saturated and; thus, does notnormally amplify the input signal. In the graph of FIG. 9, a biosignal920, which includes information on a desired bioimpedance to bemeasured, has a considerably large amplitude due to an interfaceimpedance between an electrode and the object. The biosignal 920includes all factors of an interface impedance in addition to thedesired bioimpedance.

A compensation signal 930 used to compensate for the biosignal 920 has aphase opposite to a phase of the biosignal 920. The compensation signal930 is used to reduce the factors of the interface impedance from thebiosignal 920. The compensation signal 930 is generated based on thebioimpedance of the object or an additional impedance element, and adetailed description is found with reference to FIGS. 1A through 8.

The compensation signal 930 reduces an influence on the biosignal 920due to the interface impedance by compensating for the biosignal 920. Acombination signal 940 of the biosignal 920 and the compensation signal930 have an amplitude smaller than an amplitude of the biosignal 920 andan amplitude of the compensation signal 930. Due to the combination, theamplitude of the biosignal 920 decreases by the amplitude of thecompensation signal 930. The amplifier amplifies the combination signal940. The biosignal 920 is amplified without saturating a measurementcircuit because the compensation signal 930 decreases the amplitude ofthe biosignal 920. A second reference line 950 is a common DC signalcomponent of the biosignal 920, the compensation signal 930, and thecombination signal 940. The biosignal 920, the compensation signal 930,and the combination signal 940 have an identical frequency component.

FIG. 10 is a diagram illustrating a still another example of anoperation of a bioimpedance measuring apparatus 1010, in accordance withan embodiment. The bioimpedance measuring apparatus 1010 applies anelectrical signal to an object 1080 through an electrode to measure abioimpedance of the object 1080, and measures a biosignal generated inresponse to the electrical signal flowing into the object 1080 throughanother electrode. The biosignal includes information about thebioimpedance of the object 1080.

The bioimpedance of the object 1080 is estimated based on a level of theelectrical signal applied to the object 1080 and a level of the measuredbiosignal. An interface impedance generated between the electrodes andthe object 1080 varies depending on an electrode contact environment.The bioimpedance measuring apparatus 1010 changes the electrodesapplying the electrical signal and the electrodes measuring thebiosignal. Thus, changing the electrodes applying the electrical signaland the electrodes measuring the biosignal enable reduction in aninfluence of an interface impedance that may vary depending on eachelectrode and enables a precise measurement of the bioimpedance of theobject 1080.

Referring to FIG. 10, the bioimpedance measuring apparatus 1010 includesan electrical signal generator 1020, a connection adjustor 1030, acontroller 1060, and an amplifier 1050. The electrical signal generator1020 generates an electrical signal to measure the bioimpedance. Forexample, the electrical signal is an AC signal or an AC voltage signalhaving a frequency component.

The connection adjustor 1030 adjusts connections between electrodes, forexample, 1072, 1074, 1076, and 1078, that are electrically connected tothe object 1080. The connection adjustor 1030 also adjusts connectionsbetween the electrical signal generator 1020 and the amplifier 1050. Thecontroller 1060 generates a control signal to control the connectionadjustor 1030. The connection adjustor 1030 determines, among theelectrodes 1072, 1074, 1076, and 1078, the one or more electrodes towhich the electrical signal generated by the electrical signal generator1020 is transmitted based on the control signal. In an example, theconnection adjustor 1030 includes switches, and connections between theswitches adjusted based on the control signal output from the controller1060.

The connection adjustor 1030 adjusts a connection of a first terminalgroup 1031 and a second terminal group 1041. The first terminal group1031 includes a first terminal 1032 and a second terminal 1034 to whichthe electrical signal generated by the electrical signal generator 1020is transmitted. The first terminal group 1031 also includes a thirdterminal 1036 and a fourth terminal 1038 that transmit the measuredbiosignal to the amplifier 1050. The second terminal group 1041 includesa fifth terminal 1040, a sixth terminal 1042, a seventh terminal 1044,and an eighth terminal 1046, which are connected to the electrodes 1072,1074, 1076, and 1078, respectively. The connection adjustor 1030 adjuststhe connection between the first terminal group 1031 including the firstterminal 1032, the second terminal 1034, the third terminal 1036, andthe fourth terminal 1038. The connection adjustor 1030 also adjusts theconnection between the second terminal group 1041 including the fifthterminal 1040, the sixth terminal 1042, the seventh terminal 1044, andthe eighth terminal 1046, which are electrically interfaced with theobject 1080.

For example, at a first measuring stage, the first terminal 1032 areconnected to the fifth terminal 1040, the second terminal 1034 to theeighth terminal 1046, the third terminal 1036 to the sixth terminal1042, and the fourth terminal 1038 to the seventh terminal 1044. Thus,the biosignal transmitted from the sixth terminal 1042 and the seventhterminal 1044 are input to the amplifier 1050 via the third terminal1036 and the fourth terminal 1038. At a second measuring stage,subsequent to the first measuring stage, the first terminal 1032 isconnected to the sixth terminal 1042, the second terminal 1034 to theeighth terminal 1046, the third terminal 1036 to the fifth terminal1040, and the fourth terminal 1038 to the seventh terminal 1044. Thus,the biosignal transmitted from the fifth terminal 1040 and the seventhterminal 1044 are input to the amplifier 1050 via the third terminal1036 and the fourth terminal 1038. As illustrated in the foregoing, thebioimpedance measuring apparatus 1010 measures a biosignal includinginformation on a bioimpedance a plural number of times by adjusting theconnection between the first terminal group 1031 and the second terminalgroup 1041. Further, the bioimpedance measuring apparatus 1010 preciselymeasures the bioimpedance of the object 1080 based on the biosignalmeasured the plural number of times.

The amplifier 1050 amplifies the biosignal input through the thirdterminal 1036 and the fourth terminal 1038. In one illustrative example,the biosignal is input to the amplifier 1050 in a form of a differentialsignal. The bioimpedance measuring apparatus 1010 then outputs theamplified biosignal as an output signal.

FIG. 11 is a diagram illustrating an example of an operation of abioimpedance measuring apparatus 1110 including a connection adjustor1120, in accordance with an embodiment. Referring to FIG. 11, thebioimpedance measuring apparatus 1110 includes a first electrical signalgenerator 1115, the connection adjustor 1120, a controller 1130, acompensation signal generator 1135, and an amplifier 1125. Thecompensation signal generator 1135 includes a second electrical signalgenerator 1140.

The first electrical signal generator 1115 generates a first electricalsignal to measure a bioimpedance of an object 1150. The compensationsignal generator 1135 generates a compensation signal to compensate fora biosignal generated by the first electrical signal flowing through theobject 1150. The second electrical signal generator 1140 in thecompensation signal generator 1135 generates a second electrical signalhaving a phase identical to or opposite to a phase of the firstelectrical signal. The second electrical signal is applied to the object1150 through electrodes, for example, 1170 and 1175. The compensationsignal is generated based on an interface impedance between the object1150 and the electrodes 1170 and 1175. The amplifier 1125 amplifies thebiosignal being compensated for by the compensation signal. Thedescriptions provided in FIGS. 1A through 2 pertaining to the firstelectrical signal generator 1115, the compensation signal generator1135, the second electrical signal generator 1140, and the amplifier1125 are incorporated herein.

The connection adjustor 1120 adjusts connections between electrodes 1160electrically connected to the object 1150, the first electrical signalgenerator 1115, and the amplifier 1125. The controller 1130 outputs acontrol signal to control a connection between switches included in theconnection adjustor 1120. The connection adjustor 1120 adjusts, based onthe control signal, connections between terminals connected to theelectrodes, terminals connected to the first electrical signal generator1115, and terminals connected to the amplifier 1125. The bioimpedancemeasuring apparatus 1110 measures a predetermined number of times abiosignal that includes information about the bioimpedance of the object1150. The compensation signal generator 1135 outputs the compensationsignal to compensate the measured biosignal. The compensated biosignalis then input to the amplifier 1125. A combination signal of thebiosignal and the compensation signal are amplified at the amplifier1125, and the amplifier 1125 outputs the amplified combination signal asan output signal.

FIG. 12 is a diagram illustrating another example of an operation of abioimpedance measuring apparatus 1210 including a connection adjustor1220, in accordance with an embodiment. Referring to FIG. 12, thebioimpedance measuring apparatus 1210 includes a first electrical signalgenerator 1215, the connection adjustor 1220, a controller 1230, acompensation signal generator 1235, and an amplifier 1225. Thecompensation signal generator 1235 includes a second electrical signalgenerator 1240 and an impedance element 1270.

The first electrical signal generator 1215 generates a first electricalsignal to measure a bioimpedance of an object 1250. The compensationsignal generator 1235 generates a compensation signal to compensate fora biosignal generated by the first electrical signal flowing through theobject 1250. The second electrical signal generator 1240 included in thecompensation signal generator 1235 generates a second electrical signalhaving a phase identical to or opposite to a phase of the firstelectrical signal. The second electrical signal flows into the impedanceelement 1270, and the compensation signal is generated based on thesecond electrical signal and an impedance value of the impedance element1270. The amplifier 1225 amplifies the biosignal being compensated forby the compensation signal. Descriptions of operations of the firstelectrical signal generator 1215, the compensation signal generator1235, the second electrical signal generator 1240, and the amplifier1225 may be found with reference to FIGS. 7A through 8.

The connection adjustor 1220 adjusts connections among electrodes 1260electrically connected to the object 1250, the first electrical signalgenerator 1215, and the amplifier 1225. The controller 1230 outputs acontrol signal to control a connection between switches included in theconnection adjustor 1220. The connection adjustor 1220 adjusts, based onthe control signal, connections between terminals connectedcorrespondingly to the electrodes, terminals connected to the firstelectrical signal generator 1215, and terminals connected to theamplifier 1225. Thus, the bioimpedance measuring apparatus 1210 measuresa predetermined number of times a biosignal including information on thebioimpedance of the object 1250. The compensation signal generator 1235outputs the compensation signal to compensate the measured biosignal.The compensated biosignal is then input to the amplifier 1225. FIG. 13is a flowchart illustrating an example of a bioimpedance measuringmethod, in accordance with an embodiment.

Referring to FIG. 13, in operation 1310, the bioimpedance measuringmethod generates a first electrical signal to measure a bioimpedance ofan object. The first electrical signal may be an AC signal or an ACvoltage signal having a frequency component. The first electrical signalis applied to the object through electrodes. A biosignal is thengenerated by the first electrical signal flowing through the object. Thebiosignal is generated based on the first electrical signal flowing inthe object and the bioimpedance of the object. The biosignal is measuredthrough other electrodes.

In operation 1320, the bioimpedance measuring method generates acompensation signal to compensate for the biosignal. The bioimpedancemeasuring method generates a second electrical signal having a phaseidentical or opposite to a phase of the first electrical signal. Thesecond electrical signal is an AC signal or an AC voltage signal havinga frequency component identical to the first electrical signal. Asdescribed with reference to FIGS. 1A through 8, a combinationrelationship between the biosignal and the compensation signal may varybased on the phase of the second electrical signal.

The compensation signal is generated based on the bioimpedance of theobject or an impedance element. In an example, the compensation signalis generated in response to the second electrical signal flowing throughan interface impedance between the object and the electrodes. In anotherexample, the compensation signal is generated at both terminals of theimpedance element in response to the second electrical signal flowingthrough the interface impedance.

The bioimpedance measuring method adjusts an amplitude of the secondelectrical signal that is output from a second electrical signalgenerator based on an amplitude of the compensation signal. When theamplitude of the compensation signal is determined to be higher than apredetermined threshold range, the bioimpedance measuring methoddecreases the amplitude of the compensation signal by decreasing theamplitude of the second electrical signal. Conversely, when theamplitude of the compensation signal is determined to be lower than thepredetermined threshold range, the bioimpedance measuring methodincreases the amplitude of the compensation signal by increasing theamplitude of the second electrical signal.

The biosignal is combined with the compensation signal for compensation.Therefore, an amplitude of the biosignal decreases by the amplitude ofthe compensation signal. The biosignal and the compensation signal mayhave phases opposite to each other and; thus, the amplitude of thebiosignal may decrease due to the combination.

In operation 1330, the bioimpedance measuring method amplifies thebiosignal being compensated for by the compensation signal. Thebioimpedance measuring apparatus amplifies the compensated biosignalbased on a gain of an amplifier and outputs the amplified biosignal asan output signal. The output signal output from the bioimpedancemeasuring method is post-processed, for example, filtered, and convertedto a digital signal using an ADC. The bioimpedance of the object isestimated by analyzing the digital signal. The estimated bioimpedance isprovided to a user through a display device and the like.

The units, impedance elements, controllers, adjustors, generators, andamplifiers described herein may be implemented using hardware componentscomponents. For example, the hardware components may include processors,microphones, amplifiers, band-pass filters, audio to digital convertors,and processing devices. A processing device may be implemented using oneor more general-purpose or special purpose computers, such as, forexample, a processor, a controller and an arithmetic logic unit, adigital signal processor, a microcomputer, a field programmable array, aprogrammable logic unit, a microprocessor or any other device capable ofresponding to and executing instructions in a defined manner. Theprocessing device may run an operating system (OS) and one or moresoftware applications that run on the OS. The processing device also mayaccess, store, manipulate, process, and create data in response toexecution of the software. For purpose of simplicity, the description ofa processing device is used as singular; however, one skilled in the artwill appreciated that a processing device may include multipleprocessing elements and multiple types of processing elements. Forexample, a processing device may include multiple processors or aprocessor and a controller. In addition, different processingconfigurations are possible, such a parallel processors.

It is to be understood that in the embodiment of the present invention,the operations in FIG. 13 are performed in the sequence and manner asshown although the order of some operations and the like may be changedwithout departing from the spirit and scope of the describedconfigurations. In accordance with an illustrative example, a computerprogram embodied on a non-transitory computer-readable medium may alsobe provided, encoding instructions to perform at least the methoddescribed in FIG. 13.

Program instructions to perform a method described in FIG. 13, or one ormore operations thereof, may be recorded, stored, or fixed in one ormore computer-readable storage media. The program instructions may beimplemented by a computer. For example, the computer may cause aprocessor to execute the program instructions. The media may include,alone or in combination with the program instructions, data files, datastructures, and the like. Examples of computer-readable media includemagnetic media, such as hard disks, floppy disks, and magnetic tape;optical media such as CD ROM disks and DVDs; magneto-optical media, suchas optical disks; and hardware devices that are specially configured tostore and perform program instructions, such as read-only memory (ROM),random access memory (RAM), flash memory, and the like. Examples ofprogram instructions include machine code, such as produced by acompiler, and files containing higher level code that may be executed bythe computer using an interpreter. The program instructions, that is,software, may be distributed over network coupled computer systems sothat the software is stored and executed in a distributed fashion. Forexample, the software and data may be stored by one or more computerreadable recording mediums. Also, functional programs, codes, and codesegments for accomplishing the example embodiments disclosed herein maybe easily construed by programmers skilled in the art to which theembodiments pertain based on and using the flow diagrams and blockdiagrams of the figures and their corresponding descriptions as providedherein.

A number of examples have been described above. Nevertheless, it will beunderstood that various modifications may be made. For example, suitableresults may be achieved if the described techniques are performed in adifferent order and/or if components in a described system,architecture, device, or circuit are combined in a different mannerand/or replaced or supplemented by other components or theirequivalents. Accordingly, other implementations are within the scope ofthe following claims.

What is claimed is:
 1. An apparatus to measure a bioimpedance, theapparatus comprising: a first electrical signal generator configured togenerate a first electrical signal to measure a bioimpedance of anobject; a compensation signal generator configured to generate acompensation signal to compensate a biosignal generated based on thefirst electrical signal and the bioimpedance; and an amplifierconfigured to amplify the compensated biosignal, wherein thecompensation signal corresponds to impedance of interface betweenelectrodes and the object, wherein the compensation signal generatorcomprises a second electrical signal generator configured to generate asecond electrical signal comprising a phase identical to or opposite toa phase of the first electrical signal and adjust an amplitude of thesecond electrical signal based on comparison of an amplitude of thecompensation signal and a predetermined threshold range, and thecompensation signal generator is configured to generate the compensationsignal in response to the second electrical signal flowing from theelectrodes into the object.
 2. The apparatus of claim 1, wherein thecompensation signal comprises a phase opposite to a phase of thebiosignal, and an amplitude of the compensated biosignal is smaller thanan amplitude of the biosignal before the compensation.
 3. The apparatusof claim 1, wherein a distance between two electrodes applying thesecond electrical signal into the object is shorter than a distancebetween two electrodes measuring the biosignal.
 4. The apparatus ofclaim 1, wherein the compensation signal generator further comprises animpedance element configured to generate the compensation signal basedon the second electrical signal.
 5. The apparatus of claim 1, furthercomprising: switches configured to adjust connections between theelectrodes electrically connected to the object, the first electricalsignal generator, and the amplifier; and a controller configured tooutput a control signal to control a connection between the switches. 6.The apparatus of claim 5, wherein the switches adjust, based on thecontrol signal, connections among terminals connected to the electrodes,terminals connected to the first electrical signal generator, andterminals connected to the amplifier.
 7. The apparatus of claim 1,further comprising: a first capacitor between an electrode, at which thebiosignal is measured, and a node, at which the biosignal and thecompensation signal are combined; and a second capacitor between a node,at which the compensation signal is output, and the node, at which thebiosignal and the compensation signal are combined.
 8. The apparatus ofclaim 1, further comprising: electrodes configured to conduct the firstelectrical signal or the biosignal to the object, and wherein at leastone of the electrodes interfaces with the object in electrical regions.9. The apparatus of claim 1, wherein the compensation signal generatorgenerates the compensation signal in response to the second electricalsignal flowing through the object to compensate a biosignal generatedbased on the first electrical signal flowing through the object andbased on an interface impedance between the object and electrodes. 10.An apparatus to measure a bioimpedance, the apparatus comprising:switches configured to adjust connections between electrodeselectrically connected to the object, the electrical signal generator,and the amplifier; a first electrical signal generator configured togenerate a first electrical signal to measure a bioimpedance of anobject according to the adjusted connections; a compensation signalgenerator configured to generate a compensation signal to compensate abiosignal generated based on the first electrical signal and thebioimpedance; and an amplifier configured to amplify the compensatedbiosignal, wherein the compensation signal generator comprises a secondelectrical signal generator configured to generate a second electricalsignal comprising a phase identical to or opposite to a phase of thefirst electrical signal and adjust an amplitude of the second electricalsignal based on comparison of an amplitude of the compensation signaland a predetermined threshold range, and the compensation signalgenerator is configured to generate the compensation signal in responseto the second electrical signal flowing from the electrodes into theobject.
 11. The apparatus of claim 10, wherein the switches areconfigured to determine, using a control signal of a controller, anelectrode among the electrodes to which the electrical signal generatedis transmitted.
 12. A method of measuring a bioimpedance, the methodcomprising: generating a first electrical signal to measure abioimpedance of an object; generating a compensation signal tocompensate for a biosignal generated based on the first electricalsignal and the bioimpedance; and amplifying the compensated biosignal,wherein the compensation signal corresponds to impedance of interfacebetween electrodes and the object, wherein the generating a compensationsignal comprises generating a second electrical signal comprising aphase identical or opposite to a phase of the first electrical signal,adjusting an amplitude of the second electrical signal based oncomparison of an amplitude of the compensation signal and apredetermined threshold range, and generating the compensation signal inresponse to the second electrical signal flowing from the electrodesinto the object.
 13. The method of claim 12, wherein the compensatedbiosignal comprises an amplitude smaller than an amplitude of thebiosignal prior to compensation.
 14. The method of claim 12, wherein thegenerating a compensation signal comprises: measuring a biosignalgenerated in response to the second electrical signal flowing into theobject and thereby flowing in the object, and outputting the measuredbiosignal as the compensation signal.
 15. The method of claim 14,wherein a distance between two electrodes applying the second electricalsignal to the object is shorter than a distance between two electrodesmeasuring the biosignal.
 16. The method of claim 12, wherein thegenerating a compensation signal comprises: outputting, as thecompensation signal, an electrical signal generated in response to thesecond electrical signal flowing through an impedance element, andwherein the biosignal is combined with the compensation signal todecrease an amplitude of the biosignal.